The present invention refers to the field of hexapodal machining centers comprising a stationary frame and a support, which are interconnected by six struts of adjustable length. In particular, the present invention refers to such a hexapodal machining center in which the support has provided thereon six separate articulation points for the struts.
Such hexapodal machining centers are used as machine tool structures. They are particularly suitable for machines used for metal-cutting operations, such as milling, drilling, turning or grinding or for laser machining. Such machine structures can also be used for coordinate measuring machines and in the field of manipulation technology.
Hexapodal machining centers consist, in principle, of a support, which is also referred to as a working platform in some cases, and of a stationary frame, said support and said frame being interconnected by six struts of adjustable length. This permits a movement of the working platform in all six spatial degrees of freedom, i.e. three translatory degrees of freedom and three rotational degrees of freedom.
A first hexapodal machining center is known from U.S. Pat. No. 5,401,128. This known machine tool structure consists of an octahedral machine frame comprising twelve rigid braces. At the center of the machine frame, a machining unit is arranged, which is provided with a spindle. In addition, a stationary work piece reception device is arranged in the lower part of the octahedral machine frame. Above the work piece reception device, the hexapod, i.e., a support and working platform for the machining unit, is arranged, said machining unit being e.g., a drilling spindle or a cutter spindle. Two respective hexapod struts of adjustable length have one of their ends articulated on one comer of a triangular upper frame member of the machine frame, the articulation points of the two struts on the machine frame being arranged at only a small vertical distance from one another. The articulation points of the six struts on the working platform are all positioned in one common plane. This arrangement entails a limitation of the rotational movements. In addition, the forces are not absorbed in the struts in an optimum manner, since said struts do not extend in the main load directions.
A further hexapodal machining center is known from U.S. Pat. No. 5,354,158. In the case of the hexapod shown there, two neighboring struts are articulated on a comer of an imaginary triangle on the working platform, and two other neighboring struts are articulated on the comer of a further imaginary triangle on the frame, the two triangles, which are arranged in parallel, being rotationally displaced relative to one another. The respective articulation points of the struts on the working platform and on the frame are articulated in a common plane. In addition, U.S. Pat. No. 5,354,158 discloses the measure of arranging the articulation points on the frame in two spaced planes. As far as the movability of the working platform and the absorption of the forces is concerned, this arrangement shows similar disadvantages as the arrangement according to U.S. Pat. No. 5,401,128.